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Starlight polarization provides insight into the physical mechanisms in and around the source as well as its geometry, whether or not the source is resolved. In this talk we will review mechanisms that polarize light in stellar envelopes. The observations and modeling can be used to probe the physics of the circumstellar environment as well as its relation to the ambient interstellar environment.

We describe the preliminary design of a magnetograph and visible-light imager instrument to study the solar dynamo processes through observations of the solar surface magnetic field distribution. The instrument will provide measurements of the vector magnetic field and of the line-of-sight velocity in the solar photosphere. As the magnetic field anchored at the solar surface produces most of the structures and energetic events in the upper solar atmosphere and significantly influences the heliosphere, the development of this instrument plays an important role in reaching the scientific goals of The Atmospheric and Space Science Coordination (CEA) at the Brazilian National Institute for Space Research (INPE). In particular, the CEA's space weather program will benefit most from the development of this technology. We expect that this project will be the starting point to establish a strong research program on Solar Physics in Brazil. Our main aim is acquiring progressively the know-how to build state-of-the-art solar vector magnetograph and visible-light imagers for space-based platforms to contribute to the efforts of the solar-terrestrial physics community to address the main unanswered questions on how our nearby Star works.

An extremely weak circularly-polarized signature was recently detected in the spectral lines of the Am star Sirius A. With a prominent positive lobe, the shape of the phase-averaged Stokes V line profile is atypical of stellar Zeeman signatures, casting doubts on its magnetic origin. We report here on ultra-deep spectropolarimetric observations of two more bright Am stars: β Uma and θ Leo. Stokes V line signatures are detected in both objects, with a shape and amplitude similar to the one observed on Sirius A. We demonstrate that the amplitude of the Stokes V line profiles depend on various line parameters (Landé factor, wavelength, depth) as expected from a Zeeman signature, confirming that extremely weak magnetic fields are likely present in a large fraction of Am stars. We suggest that the strong asymmetry of the polarized signatures, systematically observed so far in Am stars and never reported in strongly magnetic Ap stars, bears unique information about the structure and dynamics of the thin surface convective shell of Am stars.

Polarimetry is routinely used to characterise the surfaces of bodies in our solar system. In the near future, polarisation measurements of the starlight reflected by exoplanets will become a common and powerful tool to constrain the atmospheres and the surface properties of other worlds.

If extra-terrestial life has similar signatures as the life we know, then astronomical observations of planet Earth represent a benchmark to eventually probe bio-signatures also on other planets. In fact, linear polarisation spectra of Earthshine (the sunlight that has been first reflected by Earth and then reflected back to Earth by the Moon), allow us to detect the presence of oxygen, ozone, and water in the atmosphere of our planet. Surface properties such as fractional contributions of clouds and ocean, as well as vegetation can be inferred. Ultimately, Earthshine observations provide strong observational constraints on model predictions for Earth-like exoplanets.

In this contribution, we review the most recent observations of Earthshine by polarimetry. We highlight some advances in the interpretation and modelling of whole Earth polarisation, which will be of paramount importance to interpret possible bio-signatures of Earth-like planets in the habitable zone of nearby stars in the future.

Magnetic fields in the solar atmosphere provide the energy for most varieties of solar activity, including high-energy electromagnetic radiation, solar energetic particles, flares, and coronal mass ejections, as well as powering the solar wind. Despite the fundamental role of magnetic fields in solar and heliospheric physics, there exist only very limited measurements of the field above the base of the corona. What is needed are direct measurements of not only the strength and orientation of the magnetic field but also the signatures of wave motions in order to better understand coronal structure, solar activity, and the role of MHD waves in heating and accelerating the solar wind. Fortunately, the remote sensing instrumentation used to make magnetic field measurements is also well suited to measure the Doppler signature of waves in the solar structures. We present here a mission concept for the Waves And Magnetism In the Solar Atmosphere (WAMIS) experiment which is proposed for a NASA long-duration balloon flight.

Stellar magnetism, explorable via polarimetry, is a crucial driver of activity, ionization, photodissociation, chemistry and winds in stellar environments. Thus it has an important impact on the atmospheres and magnetospheres of surrounding planets. Modeling of stellar magnetic fields and their winds is extremely challenging, both from the observational and the theoretical points of view, and only recent ground breaking advances in observational instrumentation - as were discussed during this Symposium - and a deeper theoretical understanding of magnetohydrodynamic processes in stars enable us to model stellar magnetic fields and winds and the resulting influence on surrounding planets in more and more detail. We have initiated a national and international research network (NFN): ‘Pathways to Habitability - From Disks to Active Stars, Planets to Life’, to address questions on the formation and habitability of environments in young, active stellar/planetary systems. In this contribution we discuss the work we are carrying out within this project and focus on how stellar magnetic fields, their winds and the relation to stellar rotation can be assessed observationally with relevant techniques such as Zeeman Doppler Imaging (ZDI), field extrapolation and wind simulations.

Flux emergence phenomena are relevant at different temporal and spatial scales. We have studied a flux emergence region underneath a filament. This filament elevated itself smoothly, and the associated CME reached the Earth. In this study we investigate the size and the amount of flux in the emergence event. The flux emergence site appeared just beneath a filament. The emergence acquired a size of 24 Mm in half a day. The unsigned magnetic flux density from LOS-magnetograms was around 1 kG at its maximum. The transverse field as well as the filament eruption were also analysed.

We present the results of a numerical simulation of the corona and wind structure of the Sun-like exoplanet-host GJ 3021 using a global magnetohydrodynamic (MHD) model. The simulation is driven by the radial component of the surface magnetic field recovered with the Zeeman Doppler Imaging (ZDI) technique. We consider two different ZDI input maps, which have similar large-scale structures but different spatial resolutions and field strengths. These maps arise from different but comparable models used to fit the observed circularly polarised spectra of the star. Our simulations show that the structure of the inner corona is consistent among the considered cases. Larger discrepancies are found in the wind structure, in particular in the radial wind speed and the Alfvén surface topology. These elements can have a significant impact on the mass loss and angular momentum loss predicted for this system and in other studies based on this numerical data-driven approach.

The unification model of active galactic nuclei postulates an accreting supermassive black hole as the central engine, surrounded by a putative dusty torus. This dust absorbs the incoming radiation, re-emits it in the infrared and obscures our view of the central region at certain inclinations. We present a new set of AGN models, in which the torus is modelled as a 3D multiphase medium. These new models can explain the observed spectral energy distribution of AGNs over the entire infrared domain, including the observed silicate feature strength and the level of near-infrared continuum. A new generation of multi-phase models, based on hydrodynamical simulations, is being constructed. We will compute the polarisation structure of these physically motivated 3D torus models, and compare them to simpler smooth torus models and to the available observational data.

A combination of FTIR, normal Raman, SERS, Py-GC/MS and XRF was used to analyze commercial bistre samples to determine specific biomarkers that will allow for a rapid identification of the pigment in works of art. The results of the XRF analysis showed that potassium, calcium and iron are the main elements present. Characteristic bands belonging to phenolic components of lignin were observed in the FTIR spectra. The SERS analysis provided a fingerprint that may originate in the polymerization of the phenolic components catalyzed by the presence of the nanostructured silver surface under alkaline conditions. The Py-GC/MS analysis revealed the presence of lignin and cellulose biomarkers and a series of polycyclic aromatic hydrocarbons. The similarities observed between the commercial samples studied suggest that both originate in the same raw material, hardwood. The results demonstrate the potential of the multi-technique approach used for the characterization of this complex black-brown pigment.

Soap formation in traditional oil paintings occurs when heavy-metal-containing pigments, such as lead white, 2Pb(CO3)2·Pb(OH)2, and lead-tin yellow type I, Pb2SnO4, react with fatty acids in the binding medium. These soaps may form aggregates that can be 100-200 μm in diameter, which swell and protrude through the paint surface, resulting in the degradation of the paint film and damage to the integrity of the artwork. In addition, soap formation has been reported to play a role in the increased transparency of paint films that allows the painting support, the preparatory drawing, and the artists’ alterations to become visible to the naked eye. The factors that trigger soap formation and the mechanism(s) of the process are not yet well understood. To elucidate these issues, chemical and structural information is necessary which can be obtained by solid-state 207Pb, 119Sn, and 13C nuclear magnetic resonance (NMR). In the present study, a combination of 207Pb NMR pulse sequences was used to determine accurately the NMR parameters of lead-containing pigments and lead carboxylates known to be involved in soap formation, such as lead palmitate, lead stearate, and lead azelate. These results show that the local coordination environment of lead azelate is different from lead palmitate or lead stearate and therefore it is unlikely that lead azelate would be incorporated into an ordered structure containing lead palmitate and lead stearate. In addition, the chemical shifts of the pigments obtained are different from those of the soaps, demonstrating that 207Pb NMR is useful in characterizing the components when present in a mixture, such as a paint film. The NMR methods discussed can also be applied to other Pb-containing cultural heritage materials, electronic and optoelectronic materials, superconducting materials, and environmentally contaminated materials.

Polyphenols are chemically and biologically active compounds. Grape seed extracts (GSEs) have been widely used as a human food supplement for health promotion and disease prevention. However, there is little information regarding its application in animal feeds. An experiment was conducted to investigate the effect of inclusion of GSE at 0.025, 0.25, 2.5 and 5.0 g/kg in a wheat soya bean control diet on growth performance, protein and amino acid (AA) digestibility and plasma lipid and mineral concentrations in broiler chickens at 21 days of age. Performance was not affected by dietary treatment except in the case of birds fed the diet with the highest GSE concentration, which showed a worsening of weight gain and feed conversion. Apparent ileal digestibility (AID) of protein was significantly reduced in the birds fed the highest concentration of GSE, which also had a reduction on the AID of arginine, histidine, phenylalanine, cystine, glutamic acid and proline compared with those fed control diet. The inclusion of graded concentration of GSE in the chicken diets caused a significant linear decrease in the concentrations of plasma copper, iron and zinc. Plasma cholesterol, triglycerides and lipoproteins (high-density lipoprotein, low-density lipoprotein and very-low-density lipoprotein) concentrations were not affected by dietary GSE. In conclusion, this study demonstrated that incorporation of GSE in chicken diets up to 2.5 g/kg had no adverse effect on growth performance or protein and AA digestibility. Feed conversion was reduced and growth rate was retarded, when chickens were fed 5 g/kg of GSE. This study also indicated that grape polyphenols reduce the free plasma minerals.

The risk of dental caries increases with the use of orthodontic appliances, and it does not only depend on a patient's oral hygiene. Caries cause teeth enamel demineralization close to the orthodontic bracket. The hardness of the teeth consequently decreases, and they become brittle and loose. The type of adhesive used to fix brackets may or may not reduce enamel demineralization. Previous studies have shown that a resin-modified glass ionomer (RMGI) inhibits demineralization. The purpose of this work is to evaluate the effect of a fluoride-releasing bracket on mechanical properties of dentin and enamel on regions adjacent to orthodontic brackets bonded with RMGI and composite resin cements. The remineralization effect due to fluoride on teeth was assessed by measuring hardness and reduced elastic modulus on dentin, enamel and dentin-enamel junction (DEJ) around the bracket area by nanoindentation methods. Nanoindentation was performed using a TriboScope from Hysitron. For this purpose two sets of polished samples were prepared: one sample was a cut along a longitudinal section and the other one along a cross-section of a tooth with orthodontic treatment using RMGI. Anisotropy in the mechanical properties of the teeth is observed along each direction.

The risk of dental caries increases with the use of orthodontic appliances, and it does not only depend on a patient's oral hygiene. Caries cause teeth enamel demineralization close to the orthodontic bracket. The hardness of the teeth consequently decreases, and they become brittle and loose. The type of adhesive used to fix brackets may or may not reduce enamel demineralization. Previous studies have shown that a resin-modified glass ionomer (RMGI) inhibits demineralization. The purpose of this work is to evaluate the effect of a fluoride-releasing bracket on mechanical properties of dentin and enamel on regions adjacent to orthodontic brackets bonded with RMGI and composite resin cements. The remineralization effect due to fluoride on teeth was assessed by measuring hardness and reduced elastic modulus on dentin, enamel and dentin-enamel junction (DEJ) around the bracket area by nanoindentation methods. Nanoindentation was performed using a TriboScope from Hysitron. For this purpose two sets of polished samples were prepared: one sample was a cut along a longitudinal section and the other one along a cross-section of a tooth with orthodontic treatment using RMGI. Anisotropy in the mechanical properties of the teeth is observed along each direction.

We have performed investigations of resonance effects inside a gallium nitride one-dimensional photonic crystal slab in order to enhance the second-harmonic generated from an beam incident on the surface of the slab. Convenient conditions on the incident beam propagation direction and polarization are first identified by experimental or theoretical linear optical studies. Giant enhancements in the second-harmonic conversion have been obtained by comparison with the unpatterned GaN layer. The combined role of the resonant coupling of the fundamental field and of the second-harmonic field has been observed by rotating the polarization of the fundamental beam.

The effective ruminal degradability (ED) of dry matter (DM), crude protein (CP) and amino acids, and the effective intestinal digestibility (IED) of DM and CP of a sample of whole cottonseed was measured using in situ and rumen outflow rate techniques in three wethers cannulated in the rumen and duodenum. The microbial contamination of rumen incubated residues was corrected by a continuous rumen infusion of 15NH3 as microbial marker and rumen solid associated bacteria as reference sample. Microbial contamination resulted in an overestimation of the undegradable fraction of DM (0·291 v. 0·275; P<0·05) and CP (0·071 v. 0·037; P<0·01) and a small underestimation of ED of DM (0·500 v. 0·512; P=0·09) and CP (0·755 v. 0·779; P=0·052). A proportion of 0·1 of the ruminal undegraded CP was of microbial origin and for essential amino acids this proportion varied from 0·042 to 0·150. Differences in ED between amino acids modified the amino acid profile, with an important reduction (0·2; P<0·01) in the proportion of lysine. Apparent intestinal digestibility of the insoluble fraction of this food, measured with the mobile nylon bag technique, showed large reductions (P<0·001) with the increase of the ruminal incubation time between 0 and 72 h: from 0·392 to 0·026 for DM and from 0·851 to 0·099 for CP. These evolutions fitted an exponential function with a previous lag. The IED was estimated either by integration of these equations and those describing the ruminal degradation and rumen outflow or by incubation through the intestines of a sample pooled to be representative of rumen flow of the undegraded food. The two methods gave similar values for both DM (0·222 v. 0·203) and CP (0·659 v. 0·658).

Changes in the wheat phosphatases (phytase-Phy and acid phosphatase-AcPh) and the degradation of their substrates (inositol phosphates esters) during seed germination have been examined in two studies. Germinated grains with high phytate degrading enzymes are of potential interest in the improvement of phosphorus availability in monogastric animals. In the first study, the seeds were soaked for 1 and 14 h and germinated for 3 and 5 days with and without the addition of gibberellic acid (GA3). In the second study, the seeds were soaked for 1 h and germinated for 1, 3 and 5 days with GA3. Phytase (up to 1800 and 1573 U/kg) and acid phosphatase (up to 13 115 and 10 154 U/g) activities and IP6 (6·96 and 7·67 mg/g), IP5 (0·40 and 0·60 mg/g) and IP4 (0·04 and 0·04 mg/g) were detected in ungerminated spring and winter wheat, respectively. The germination process caused a significant increase of Phy and AcPh activities in spring (up to 275 and 235%) and winter wheat (up to 250 and 329%) and a reduction in the phytate phosphorus content (up to 35 and 64%, respectively). Phytate phosphorus content was affected in both spring and winter wheat by the soaking time. Finally, during the course of germination, IP6 and IP5 were more rapidly degraded in winter wheat (62 and 62%) than in spring wheat (32 and 29%), and IP4 was only a short-living intermediate, which was increased during hydrolysis and degraded to IP3. In conclusion, the germination process caused a significant increase of Phy and AcPh in spring and winter wheat, which was accompanied with a significant reduction of phytate phosphorus content and an increase in the content of lower inositol phosphates.

A study was conducted to determine the effect of the feed intake on the chemical composition of bacteria associated with the solid (solid-associated bacteria; SAB) and liquid (liquid-associated bacteria; LAB) fractions of rumen digesta, the digestive passage kinetics and their relationships. Whole rumen contents were sampled after a period of continuous infusion of 15NH3 from four ruminally-cannulated wethers provided successively with a hay–concentrate diet (2: 1 w/w on a DM basis) at two rates of feed intake: 40 and 80 g DM/kg body weight0·75. SAB had a higher content of organic matter and total lipids (P < 0·001) and a similar N content as compared with LAB. The concentration of purines and 15N was lower (P = 0·011 and P < 0·001 respectively) in SAB than LAB, whereas the opposite was observed for the concentration of amino acids (mg/g DM; P = 0·031). An increase in feed intake produced an increase in the N (P = 0·034) and purine (P = 0·066) concentrations in bacteria and a decrease (P = 0·033) in their amino acid concentrations. Significant increases of rumen outflow rates of liquid and particles were also observed with increased feed intake. Rates of rumen outflow showed positive and negative linear relationships (P < 0·001) with the purine: N ratio and the proportion of amino acid on total N of bacteria respectively. SAB contained significantly higher proportions of leucine, isoleucine, lysine and phenylalanine and lower proportions of alanine, methionine and valine than LAB. The increase in feed intake also induced significant changes in the amino acid profile of bacteria, increasing arginine and methionine and decreasing alanine and glycine proportions. Results show that the outflow rate of rumen contents is a major factor in determining the proportion of nucleic acids and protein in rumen bacteria and explains some of the differences observed between LAB and SAB.

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